What’s the Salmon Survival Rate at Each Life Stage?

Duration

20-40 min for work-

sheet activities

5 min daily to record

mortality, 10 min to

calculate overall mortal-

ity at different stages

1 hour to create visual

representation of survi-

vorship

NGSS

LS1B: Growth and

development of organ-

isms

LS1A Interdependent

Relationships in Ecosys-

tems

LS4B. Natural Selection

ESS3.A Natural re-

sources

ESS3.C Human impacts

on Earth Systems.

Science and Engineering

Practices:

Obtaining, evaluating,

and communicate

information

Analyzing and interpret-

ing data

Developing and using

models.

Materials

White tray

Camera

Internet access

Salmon bag!

Art supplies (butcher

paper, scissors, hole

punch, glue)

Copies of handouts in

this packet

Students will:

Develop a strategy to confirm the number of eggs in the tank.

Record daily mortality in the salmon tank, and calculate overall sur-vival rate for egg, alevin, and fry life cycle stages under different rear-ing conditions (stream, hatchery, and tank).

Illustrate survivorship with a visual representation / model.

Evaluate which mortality factors have the biggest influence on survi-vorship, identify ways to prevent salmon loss, and adopt one steward-ship practice as a class to help salmon.

Objectives

All student participants in Salmon in the Classroom can observe salmon develop from one life stage to the next, and experience the salmon life cycle firsthand. Many students learn to identify these stages by name: eggs, alevin, fry, fingerlings, smolt, adults, spawners. Your class may also be familiar with factors that threaten salmon survival, such as predation, poor water quality condi-tions, or fishing. But which life cycle stage is the most frag-ile? And how are these threats different for wild salmon, versus those raised in a pro-tected hatchery envi-ronment? This activity introduces the idea that survivorship rates vary depending on the life cycle stage and rearing environment.

Making Connections

Students calculate Coho survival rate at different life stages, and compare survival rates across three different rearing environments: rivers, hatcheries, and their own salmon tank.

Summary

Page 2 What’s the Salmon Survival Rate at Each Life Stage?

Your Redd Tank

In a river nest of

2000 wild Coho

eggs, only 300

survive to become

fully developed

alevin…

Roughly the same

number that’s in

your tank!

Wild Coho salmon typically lay 2500 eggs in their gravel streambed nests, but only about 15% of those eggs will survive to hatch and become fully developed alevin. Rivers and streams are dynamic environ-ments, and wild young salmon at the egg and alevin stages are subject to countless factors that threaten their survival: predation, silt covering and suffocating the eggs, low dissolved oxygen, pollution, and block-ages in the stream. Hatcheries eliminate those threats by raising eggs and alevin indoors, in very stable and protected environ-ments. Spawning and raising eggs at a hatchery dra-matically increases salmon survival at the early stages, often with 90% surviving through the alevin stage. However, once hatchery-raised fry and smolts are re-leased from their protected existence, they may not fare as well as their wild counterparts. And ultimately, very few from either environment return to spawn in their natal streams.

Background

Warm up:

Do you know how many eggs a Coho lays in its nest? It varies by year due to environ-mental conditions: they might lay 2800 in a good year, or 2200 in a drought year.

When a Coho deposits 2500 eggs into a river nest, how many of those will survive to come back and lay their own eggs? Very few! In a normal year, we may expect only 1 or 2 to return. Show students your fancy salmon bag! (Left)

What are some reasons salmon eggs might not hatch in the wild? Some eggs are not fertilized, some get washed away or covered with silt, the water may not have enough oxygen, or eggs may be eaten by birds. (Watch bouncing egg video, above)

Do you think those same factors affect eggs raised at a hatchery? Can birds get in-side the incubation room? What about once the hatchlings are moved to outside ponds? Watch the Lewis River Hatchery video showing egg / alevin incubation trays (above). Hatcheries provide very stable environments for eggs to develop, and many major threats are virtually eliminated. Nets protect fish from predation even in outdoor ponds (aside from the occasional sneaky river otter).

How many eggs do you think are in our tank? How many do you think will survive to release day? Record student responses!

Procedure

Open the zipper

on the spawning

salmon to show

thousands of

“eggs!” Red

beads indicate

how many sur-

vive their incredi-

ble journey.

Check-out this

salmon bag as

part of the

Salmon Trunk.

Just ask!

Angie Stefani shows us the incubation trays at

Lewis River Hatchery. How do hatcheries make

it easier for eggs to survive? Can predatory

birds get inside the incubation rooms?

Wild salmon may be exposed to hazardous

conditions before they are even born! Watch

the video of these eggs swirling around as adult

Activity: Part 1. Confirm the number of eggs in the salmon tank.

The first step in calculating survival rate is knowing how many you start with!

You were right to be suspicious! We always tell you that we gave you 250 eggs, but have you ever actually counted them? Neither have we! But we HAVE weighed them!!! As a class or for independent work, have students use the worksheet “Who wants to help count 14,000 eggs” and the “Fish and Egg Disposition Ticket” to get a better idea of how many eggs are actually in your tank… and how we get around counting all 14,500 of them!

“Eggs are more cooperative when it comes to being counted.” Do you ever scream curses on fish release day, when

you’re trying to catch and count approximately 250 squirming, darting fry out of your tank? SITC teacher Mike Clapp doesn’t! Find out how he engages students in egg delivery by e knows exactly how many salmon are in his tank (below), and use the “Aerial Biological Survey of Salmon Eggs in the Tank” worksheet to do this with your students:

When I get the eggs back to my classroom, I first pour them into a container with water and take a pic-ture before releasing them into the tank. I'll then print out copies of the picture (black & white photo cop-ies work fine) and have students count the number of eggs. It is interesting to see the different values and strategies students use to count the eggs in the picture. We'll then compare answers. (Opportunity to do some math analysis - range, mean/median/mode, ...) It is interesting to see just how many eggs we do receive. Inquiring minds want to know! Interestingly, there is an Oregon Field Guide episode where they do a similar thing using aerial photos to count nesting sea birds on the Oregon Coast. I also use this information to determine the final number of salmon I release in the spring. I'll keep track of eggs that don't develop and the salmon that don't make it. I'll subtract these from the number of eggs I received to determine my final release total. It is much easier than trying to count the hundreds of salmon when I scoop them out of the tank. The eggs are definitely much more cooperative when it comes to being counted. —Mike Clapp, CAM Academy

Watch the first 2:40 of the Ore-gon Field Guide Episode. Aerial photos in action!

Page 3

Activity: Part 2. Calculate survival rates for different life cycle stages and rearing environments.

Record daily mortality in the tank by marking down any eggs, alevin, or fry that that you remove from the tank. You can simply add a “mortality” column to your ATU chart (see Table 1. Salmon Count and ATU Chart). Read “How many Hens does it take to make 14,500 salmon eggs?” and “Only the strong survive” to guide a discussion about what this table would look like if we extended it from the time of egg deposition to returning as a spawner!

Watch the intake of the waterfall filter intake, and the powerhead pump for any mortality, since babies may get stuck there. If students find this to be a morbid task, they may be comforted by the fact that at this life stage survival rates in the tank are much higher than salmon would experience in the wild!

Once all the eggs hatch, you can calculate the survival rate in the tank for the egg stage (see 10.1 Salmon Survival

and Excel sheet for help). Once all the alevin have buttoned up, you can calculate the survival rate for the alevin. By the time you release the fry, you’ll have survival rates for all life stages that your students were able to observe.

In the meantime, calculate survival rates for wild and hatchery-raised Coho using the “ 10.1 Salmon Survival“ hand-

out. This allows you to see the survival rates of different life cycle stages and different rearing environments, side-by-side.

Part 3. Illustrate survivorship with visual representations.

Next, have students create a model or visual representation of this data. They can graph rates for wild and hatchery-raised fish using the “10.0 Salmon Survival“ handout, and add their own tank data as it becomes avail-able. Alternately, this could turn into a more creative art project. See “Natural Survival Pyramid” for a jumping off point… Get your Martha Stew-art on!

Part 4. Identify the mortality factors for each life cycle stage, and ways to help salmon overcome those factors.

Use the “Salmon Life Cycle” worksheet (courtesy of Mike Clapp!). Students identify salmon “helps and hazards” for each life cycle stage.

If your students already do a salmon life cycle journal, consider

incorporating survival rates at each life stage, hazards to which each life stage is particularly vulnerable, and ways people can help minimize those specific threats.

Based on their calculations and comparisons, which threats do

students think are the biggest influence on overall salmon sur-vival? What stewardship practice might help salmon the most? Is it different for different life stages? Why is that? Identify one stewardship project to complete as a group: plant-ing trees, improving salmon habitat, and storm drain stenciling have all been done by SITC classes!

Page 4

Name:______________

Date:______________

Who wants to help count 14,000 eggs???

Each year the Lewis River Hatchery donates over 14,000 Coho eggs to be raised in schools.

Eggs for each school are placed inside a knee high stocking, stacked carefully into a cooler, and

distributed to about 50 teachers in Clark County. The number of schools in the program and

the total number of eggs raised can vary each year.

Look at the Fish and Egg Disposition Ticket (over). What is the total number of eggs

picked up from Lewis River Hatchery in 2016?________

The total allotment (or number) of eggs is divided

amongst all the teachers. This year, 52 schools will

receive eggs. How many eggs should each school re-

ceive? _________

Your teacher was told that each school receives about

250 salmon eggs. But your teacher is suspicious… did

anyone really count all these eggs? Counting out

14,000 eggs one-by-one would take a LONG time! Can you think of a faster way to divide

up the total allotment among the 52 teachers? Describe your idea here:

Look at the Fish and Egg Disposition Ticket again. Hatcheries always keep track of #

of fish per pound. This ratio determines when fish can be “planted” or moved to a dif-

ferent location. What is the number of salmon eggs per

pound? ____________

Roughly how much does each salmon egg weigh? ________

How much did each school’s stocking weigh? ________

Congratulations! You have just completed the same math problem a hatchery

worker does for their job. Next year you can volunteer to help with egg pickup

and do the math for us!

Name:______________

Date:______________

Aerial Biological Survey

Of Eggs in the Salmon Tank

Take a look at the eggs on the gravel of your salmon tank. Be careful not to lift the black cover-

ing for more than a few seconds, so that you don’t disturb the developing eggs.

How many eggs do you think are in the tank? ____________

What is most challenging about counting the eggs in your tank?

_______________________________________________

Wish you had more time to count? Too hard to see all the way to the back of the tank? Welcome

to the world of a field biologist! Biologists often deal with a number of constraints, such as time,

money, and ability to access what they want to study.

For example, each year seasonal biologists survey the number of

salmon redds, or nests, in streams to get important information about

spawning patterns. Usually these surveys are conducted by someone

walking along the stream bank. Sometimes this method is impossible,

and instead people conduct aerial surveys to count salmon redds from

a helicopter. (Drones can capture images of salmon redds, too!)

Aerial surveys are used for all kinds of things in science, including population estimates of

whales, nesting seabirds, and even marine debris floating on the ocean’s surface!

How can using an aerial photo make a scientist’s work easier?

______________________________________________________

Look at your aerial photo. Counting this many eggs might be difficult! Can you come up with

any strategies to make this easier? _________________________________________

How many eggs do you count in your aerial photo? __________________

What is the class average? _______________

CAM Academy

Salmon in the Classroom—2015 https://sites.google.com/a/battlegroundps.org/cam7-8science/cam-7-science/salmon

Table 1. Salmon Count and ATU Chart

How many Hens does it take to make 14,500 salmon eggs???

If you were so inclined, you could complete this chart all the way back to the spawn-ing adults. Hatchery workers fill out daily “Pick Sheets” tracking mortality of eggs, along with temperature units. Lewis River Hatchery knew we needed 14,500 eggs for the SITC school allotment, and they assumed a 10% loss in eggs due to fungus, “blanks,” and not surviving the shocking process. They planned to take 15,960 eggs during spawning to get 14,500 eyed eggs. They assumed a fecundity of roughly 2700 eggs per female (or “Hen”), so they planned to use 6 females for our total school allot-ment. However, eggs counts per female were lower than expected at roughly 2200 eggs per female, so actually it took 9 Hens to make our allotment this year! Female spawning salmon are called “Hens” and male spawners are called “Bucks” by hatchery workers, because “Female” and “Male” sound too similar when you’re work-ing really fast and throwing fish around in a loud river.

Salmon Box Curriculum 43

Use the numbers below to find out how many salmon survived. Use this pagefor your work.

1. A salmon deposited 5,500 eggs in a redd.

2. Five hundred eggs were not fertilized.

3. Sixty were washed out of the gravel during a flood.

4. Mud from a clearcut eroded into the stream and suffocated one thousand, twohundred.

5. Three hundred alevins died because they could not get enough food.

6. After the alevins developed into fry, six hundred fish were eaten by other fishin the stream.

7. Forty-one were eaten by birds.

8. As they neared the ocean, 260 salmon we caught in a pool where they got toohot because of thermal pollution from a coal-fired power plant.

9. In the ocean, 1,500 were eaten by bigger fish.

10. Seals ate 95.

11. Fisherman caught 556.

12. As the salmon returned to their spawning stream, bears ate 180 of them.

13. Three were unable to jump a waterfall.

14. The rest of the salmon spawned.

15. HOW MANY SALMON WERE LEFT TO SPAWN?

Only the Strong Survive

○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Adapted fr om various sour ces, including Fish and Fisheries , B. Mickelson and N. Barr , eds. This unit fr om the Alaska SeaWeek Curriculum Series can be obtained by contacting UA-Fairbanks, 304 Eielson Building, Fairbanks, 99775-5040.(907) 474-6707

Name:student sheet

230 SALMONIDS IN THE CLASSROOM: INTERMEDIATE UNIT 10: Review—The Salmon Life Cycle 231

Wild coho salmon survival

Stage ofdevelopment

Number Deaths Number of survivors

Survival rate

Causes of death

Eggs/Alevins 2,500 2,125 375 15% • Unfertilized eggs• Gravel movement• Low oxygen in water• Drastic changes in water temperature• Pollution and/or sedimentation• Disease• Predators• Poor habitat conditions

FryEggs/Alevins

375 245 30 • Lack of adequate food or space• Predators (rainbow trout, doll var-den, char, grayling trout, sculpin, steelhead trout, ducks, merganser, tern, kingfisher)• River blockage or diversion along migration route• Pollution

HANDOUT 10.1

Salmon SurvivalA single pair of salmon produces thousands of

fertile eggs, but the number of adult salmon that

will survive depends on harvest levels and salmon

habitat, especially ocean conditions.

After release, hatchery fish may not survive as

well as wild ones, and they compete with wild

populations for food and safe places to grow.

Hatcheries cannot remedy the loss of fish habitat,

but they remain tools that managers can use to

help support endangered salmon populations.

The chart below shows the average number of

salmon that survive at each stage of their life

cycle, or the survival rate. (The chart uses

average numbers for coho salmon. The numbers

for other species of salmon are different, but they

follow the same general pattern. The survival

rate at each stage can vary considerably from the

average.)

This chart uses average numbers for coho salmon. The numbers for other species of salmon are different, but they follow the same

general pattern.

232 SALMONIDS IN THE CLASSROOM: INTERMEDIATE UNIT 10: Review—The Salmon Life Cycle 233

HANDOUT 10.1

Salmon Survival

Fish hatcheries can greatly increase the number of salmon that survive the early stages. However, the smolts from hatcheries may not survive as well as wild smolts. Only a few grow to become adults

and return to spawn in their home stream or lake.

The next chart shows the number of salmon that survive when the eggs are reared in a hatchery.

Wild coho salmon survival (cont'd)Stage ofdevelopment

Number Deaths Number of survivors

Survival rate

Causes of death

Smolts 30 25.5 4.5 • Predators (other fish, killer whale)

Adults 4.5 2.5 2.0 • Harvesting (sport, commercial, Aboriginal food fishery)• Predators

Spawners 2 2 0 • Water levels too high or low• Predators (bears, otters, minks, birds)• Obstructions (dams, rock slides, log jams)• Diseases• Death after spawning

Hatchery coho salmon survivalStage ofdevelopment

Number Deaths Number of survivors

Survival rate

Causes of death

Eggs/Alevins 2,500 250 2,250 • Unfertilized eggs• Failure of hatchery systems• Disease

Fry 2,250 450 1,689 • Disease• Predators (otters, minks, birds)

Smolts 1,689 1,530 253 • Predators (other fish, killer whale)

Adults 253 162 111 • Harvesting (sport, commercial, Aboriginal food fishery)• Predators

Spawners 111 111 0 • Water levels too low or too high• Predators (bears, otters, minks, birds)• Obstructions (dams, rock slides, log jams)• Diseases• Death after spawning

232 SALMONIDS IN THE CLASSROOM: INTERMEDIATE UNIT 10: Review—The Salmon Life Cycle 233

Hatchery coho salmon survival1. Use graph paper and coloured pencils or a computer graphing program to create a graph showing the

number of survivors at each stage of a natural salmon cycle.

2. Add a graph showing the number of survivors at each stage of a hatchery salmon cycle.

3. What does the difference between the charts show? ______________________________________

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

4. The survival rate is the percentage of the original eggs that remains alive at each stage. You can calculate the survival rate for each stage using this formula:(number of survivors) / (number of eggs) x 100For example, the survival rate of natural eggs and alevins is 15% (375/2500 x 100).

5. Calculate the survival rate after each stage in the natural life cycle. Add it to the chart.

6. Calculate the survival rate after each stage in the hatchery life cycle. Add it to the chart.

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

7. At which stage is the difference between the natural and the hatchery survival rate greatest?

8. If salmon lived at the hatchery survival rate, what would happen to the number of salmon?

Explain your answer. ________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

HANDOUT 10.1

Salmon Survival

This alternate ver-sion of the “10.1 Salmon Survival” Worksheet allows students to see the survival rate num-bers for all 3 rearing environments side-by-side.

Download editable Excel Sheet here: www.columbiasprings.org/programs/salmon-in-the-classroom/teacher-curriculum-and-resources/

Wild Coho Salmon Survival

Life Stage Number at beginning

Deaths Number of survi-

vors

Survival Rate %

Causes of Death

Eggs / Alevin

2500 2125 375 15%

Fry 375 245 30 Smolt 30 25.5 4.5 Adult 4.5 2.5 2 Spawner 2 2 0

Hatchery Coho Salmon Survival

Life Stage Number at beginning

Deaths Number of survi-

vors

Survival Rate %

Causes of Death

Eggs / Alevin

2500 250 2250

Fry 2250 450 1689 Smolt 1689 1530 253 Adult 253 162 111 Spawner 111 111 0

Salmon Tank Coho Survival

Life Stage Number at beginning

Deaths Number of survi-

vors

Survival Rate %

Causes of Death

Eggs / Alevin

250??

Fry Smolt Adult Spawner

Salmon Box Curriculum 41

Natural Survival Pyramid

○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Objectives:• Create a visual depiction of the number ofsalmon that survive at each life stage.• Understand that most salmon eggs will notsurvive to adulthood.• Name two natural threats to salmon.• (for older students) Calculate the percentageof fish that do and do not survive at each lifestage.

Materials:• large sheet of butcher paper• construction paper (5 colors)• yard stick• scissors• glue• colored pens• hole puncher

Background:Even under ideal conditions, most salmoneggs will never survive to maturity. Thefragile eggs die for many reasons: low watertemperatures, predation, disease, fungus, lackof fertilization, shifts in gravel, and siltation.Flooding may also wash the eggs away; adrought can cause the eggs to dry up.

Goal:•To understand the mathematics behindsalmon survival at each life stage

Fr om California's Salmon and Steelhead , Diane Higgins, ed. Lesson contributed by Neil W oodward, W illits. CA

Young fish must also compete for food andspace, which may act as limiting factors. Asstreams diminish in the summer, so doesavailable habitat. Water temperatures mayrise too high. The fry stage is the toughest;only five percent will survive.

Preparation:1. Draw a triangle on the butcher paper withsides of 40 inches. Divide the triangle intofive sections, as shown.

2. Make the eggs by using a hole punch oncolored paper (pink or orange is best). Savethe punched out circles to use as eggs.

Procedure:1. Explain to the students that they will bemaking a picture that shows how the numberof surviving fish becomes smaller and smallerat each life stage. They will start with 2,000eggs. Make predictions on how many theythink will survive.

2. Two thousand circles to represent eggswould be a little much, so one circle willrepresent 100 eggs. For the same reason, onefry picture will represent 20 fry. Help stu-dents calculate how many circles they mustuse to represent 2,000 eggs. How many frypictures for 200 fry?

3. Decide on your color coding, for example,orange eggs, green fry, blue smolts, silveradults, red spawners. Have the students countout the eggs and then draw and cut out theother fish forms.

lesson plan

42 Salmon Box Curriculum

4. Glue the eggs and fish onto the pyramid.Make a key that shows the relationship be-tween color and stage. Also, indicate that 1circle = 100 eggs and 1 fry picture = 20 fry.Write the number of fish at each stage next toeach section, as shown.

5. As you put the pyramid together, discusswhy so many of the fish die. What kills them?What would happen if they all lived andreturned to spawn? Why does the female fishlay so many eggs? How would survival beaffected if the parents were around to some-how protect the young fish?

6. Have older students calculate what percent-age of the fish survive through each life stage.What percentage die at each life stage? (90%die as eggs or alevin, 95% of the fry will diebefore smolting, 50% of the smolts will notreach adulthood, and 40% of the adults willnot survive to spawn).

7. A very large salmon may lay as many as10,000 eggs. Have students figure how manywill remain at each life stage, using the samepercentages as before.

2,000 EGGS one circle = 100 eggs

200 FRYone fish =20 fry

10 SMOLTS

5 ADULTS

3 SPAWNERS

M. Clapp/BGSD – life_cycle.pdf

1. location:

4. location:

6. location:

5. location:

2. location:

3. location:

Salmon Life Cycle

egg

stream to estuary & ocean

Class: Name

Assignment: Salmon Life Cycle Date

Instructions1. Label and illustrate (use color) the stages of a Pacific salmon’s life cycle.2. On the back, create a list of salmon helps and hazards.

7. location:

migrating adults

M. Clapp/BGSD – life_cycle.pdf

InstructionsIn the table below, name the seven stages of a salmon’s life. Then, create a list of environmental helps (natural events or human actions that benefit salmon or increase their chances of survival) and hazards (natural and manmade threats to survival). There should be at least one help and one hazard for each stage of the salmon’s life. Be specific. If you state a salmon is killed or threatened, tell what (cause of threat), where (location of threat), and how (type of harm). For example: “Salmon smolts are eaten (how) by Caspian terns (what) as they enter the estuary (where).” Or, “Erosion (what) smothers (how) eggs in the stream gravel (where).” Do the same for helps. Be specific. Identify the environmental help and indicate how it benefits the salmon. Example: “Clean (what) streams (where) help fry find food to eat (how). Do not include salmon adaptations like gills, yolk sacs, coloration, ....

7

6

5

4

3

2

1

HazardsHelpsStage

egg